Introduction
Just like any other type of spring, gas springs have spring curves that define the force v. deflection characteristic for the spring. In the field of gas springs and especially those used in vehicles, it is well known that it is often advantageous for the gas spring curve of the gas spring to be able to be changed. Accordingly, our '144 application extensively describes the advantages of a gas spring performing according to a gas spring curve selected—by the rider—from a number of different spring curves (i.e., “softer” and “stiffer”). The need for a gas spring to perform according to a gas spring curve selected—by the rider—from a number of different spring curves (i.e., “softer” and “stiffer”) is also generally discussed in the prior art, such as in US Pub 2005/0116399.
It is highly desirable that the gas spring curve of the gas spring should be able to be easily changed by the rider on-the-fly. Typically, for example, in the bicycle arts, a successful “on-the-fly” adjustment should: (1) be able to made without tools; (2) require small controller manipulations (e.g. short angular knob rotations); (3) require low forces/torques to manipulate the controller; and (4) be capable of being made very quickly (for example, in one or two seconds) and without the rider having to stop or dismount.
Discussion of Prior Art
The prior art includes a number of adjustable-volume gas-pressurized devices that, while capable of being adjusted to provide various gas spring curves, are not capable of, or conducive to, easy on-the-fly adjustment.
For example, a number of adjustable gas spring designs require rotating an adjustment cap against a significant amount of torque for a full 360° or more, to change the gas chamber volume. As examples, see, e.g. Risse Racing (“Remote Adjustable Gas Chamber”); Showa (U.S. Pat. No. 5,346,236 and Showa Advertisement, Mountain Bike 22-23 (June 1994)); Berthold (U.S. Pat. No. 5,957,252); Rockshox (U.S. Pat. No. 6,095,541); and SRAM (US Pub. 2005/0116399). (For completeness, we note here that the rotation adjustment described in SRAM '399, besides changing gas chamber volume, also changes total fork travel.)
Additionally, in the DHX 5® shock absorber made by FOX FACTORY, INC., the assignee of the current invention, adjusting the independent bottom-out resistance, which operates according to a gas spring curve as generally described in paragraphs [0079]-[0080] of our WO2006/054994, requires a significant amount of torque to rotate the control knob.
It is also known to those skilled in the art that by changing the volume of the oil in the damper, the air spring response can be adjusted. See e.g. Showa Advertisement (referred to above) (referring to common prior art practice: “Have you ever changed the oil volume in your suspension? Does it take a great deal of your time?”); Rick Sieman, “Do It Yourself Tech—Dial in Your Own Forks” (www.offroad.com/dirtbike/tech/forks/); “How to Improve the Ride and Suspension Performance of Cruiser Motorcycles” (www.motorcyclecruiser.com/tech/improve_ride_suspension_performance/); “Suspension Tuning Guide—Learning the Lingo” (www.sportrider.com/tech/146.sub.—0006_lingo). With this method, depressurization of the gas spring is required before the oil may be added or removed and then re-pressurization of the gas spring is required before use.
Other methods that require depressurization and re-pressurization of the gas spring during the course of making the spring curve adjustment are: (a) rotating internal parts using an Allen-wrench (e.g. 1998 Rockshox SID); (b) adding a volume spacer (e.g. 1999-2000 Rockshox SID); and (c) re-locating an internal volume plate (Cane Creek AD-10 and AD-12 rear shocks and U.S. Pat. No. 5,775,677).
When a rider has to exert this much effort and labor to make spring curve adjustments, the gas spring curve adjustment cannot be considered an on-the-fly adjustment—no less a practical on-the-fly adjustment.
As described in our '144 application, spring curves in a gas spring can be changed by altering the initial gas chamber volume. Increasing or decreasing the initial gas chamber volume softens or stiffens, respectively, the gas spring curve. The '144 application describes the theory and formulas underlying how varying gas chamber volumes effects spring curves. Note also that gas springs are sometimes referred to air springs because the gas they use is often air.
Selectively placing main and auxiliary gas chambers in fluid communication with each other to alter the total gas volume subject to compression and therefore the gas spring curve of the gas spring has been widely used in various constructions in automobiles (U.S. Pat. Nos. 1,094,567; 4,206,934; 4,534,580; 4,592,540; 4,598,929; 4,613,116; 4,616,811; 4,635,906; 4,651,977; 4,653,735; 4,659,070; 4,697,796; 4,673,171; 4,735,401; 4,746,106; 4,768,758; 4,773,635; 5,915,674; 6,883,810; 6,698,730; 6,708,803; JP61-1135808; DE 10236621; DE 3233160; and DE 4018712). Additionally, in an automotive application, JP61-1135808 teaches that a main chamber may be used in combination with two remote gas chambers to provide for three different spring curves.
However, the bulky, motor driven, electronically controlled, multi-component, and external (to the gas spring housing) devices disclosed in much of the previously mentioned automotive prior art and used to achieve this functionality are not conducive to un-powered devices, compact and lightweight packaging, and/or incorporation into smaller adjustable-volume gas-pressurized devices, such as used in bicycle or other two-wheeled vehicle suspensions.
Indeed, as compared to the automotive solutions described above, there has been much less success in finding innovative ways to provide two-wheeled vehicle riders with the ability to easily and quickly change the gas spring curve of adjustable-volume gas-pressurized devices on-the-fly. Currently used methods remain labor or effort intensive and not are conducive to on-the-fly adjustment. As mentioned above, the most widely used current two-wheel vehicle solutions involve:
1. Rotating an external knob or nut against significant torque, e.g. Showa; Risse Racing; Rockshox ('541); SRAM ('399); Bethold (U.S. Pat. No. 5,957,252); FOX DHX (WO06/054994);
2. Adding or removing oil after depressurization of the gas spring, e.g. various sources mentioned above;
3. Rotating an internal part to increase or decrease the gas chamber size after depressurization of the gas spring and requiring use of an Allen wrench, e.g. 1998 RockShox SID;
4. Adding a “volume spacer” to increase or decrease the gas chamber size after depressurization of the gas spring, e.g., 1999-2000 RockShox SID; and
5. Re-locating an internal ‘Volume Plate’ to increase or decrease the gas chamber size after depressurization of the gas spring, e.g., Creek AD-10 and AD-12 rear shocks (See U.S. Pat. No. 5,775,677).
Accordingly, the current invention, as will be described below, provides very practical and simple ways for two-wheeled vehicle riders to have the ability to easily and quickly change the gas spring curve of adjustable-volume gas-pressurized devices on-the-fly.